The Red Army played a crucial role in the Spanish Civil War, supplying over 1,000 aircraft, 900 tanks, 1,500 artillery pieces, 300 armored cars, hundreds of thousands of small arms and 30,000 tons of ammunition to the Republican cause.

Soviet participation in the Spanish Civil War was greatly influenced by the growing tension between Stalin and Adolf Hitler, the leader of Nazi Germany and an avid supporter of the fascist forces of Francisco Franco. Nazi-Soviet relations were tempered by Hitler's personal hatred of the people of East Europe and by the longstanding ideological feud between fascism and communism.

"... a little more than 2,000 Soviet volunteers fought and worked in Spain on the side of the Republic throughout the whole war, including 772 airmen, 351 tank men, 222 army advisers and instructors, 77 naval specialists, 100 artillery specialists, 52 other specialists, 130 aircraft factory workers and engineers, 156 radio operators and other signals men, and 204 interpreters".

"... a little more than 2,000 Soviet volunteers fought and worked in Spain on the side of the Republic throughout the whole war, including 772 airmen, 351 tank men, 222 army advisers and instructors, 77 naval specialists, 100 artillery specialists, 52 other specialists, 130 aircraft factory workers and engineers, 156 radio operators and other signals men, and 204 interpreters".

Yes, in gold. See Arms for Spain: The Untold Story of the Spanish Civil War, By Gerald Howson, John Murray, 1998,

The Spanish gold reserves worth $518 million (1936 value) were sent to the Soviet Union for safekeeping - most of it was used for arms purchases. Howson calculates that Stalin defrauded the Republic by at least $51 million. Some of the armaments the USSR supplied were top of the line stuff, and some was not - e.g. seemingly whatever foreign made artillery the Red Army had in its' storage depots.

That being said, the Republic was defrauded by most of the gun runners they tried to use. The French didn't exactly supply much up to date equipment either. The Poles generously sold them perhaps 50 FT-17 tanks of which only 5 were in running condition. etc

Probably the best source of information on the Internet about the Soviet aid to the Republican Spain you can find here:

http://www.gutenberg-e.org/kod01/frames/fkodimg.html

I am surprised nobody has listed this link yet.

Poland was the second largest supplier of armaments to the Spanish Republic during the Civil War (after Soviet Union), despite the fact that Poland officially supported only the Franco rebels.

http://www.dws.org.pl/viewtopic.php?f=51&t=125868&st=0&sk=t&sd=a

Poland dispatched its shipments by sea from its own port of Gdynia, and the nearby Free City of Gdansk. Could the shipments from the latter port been pilfered and/or sabotaged by the local Germans? After all the Chinese pilfered the Soviet shipments to Vietnam during the Vietnam wars, so I think that was possible.

As for the Soviets keeping their gold, vast majority of it was plundered in the New World.

In fact, as already September 26, 1936 from Feodosia in Cartagena came the first vessel, which would then be specified by the transport Y-1 - Spanish tanker the Campeche, on board, in addition to oil in the cargo tanks, and was the first batch of weapons transferred by the Soviet side: six English 114 -mm howitzer Mk I and 6000 shells for them, 240 German 16-linear-propelled grenades and 100 thousand grenades to them, 350 heavy machine guns St. Etienne, Colt and Vickers, 200 light machine guns MG 08/15 and Hotchkiss, 21347 rifles (2000 German 7.92 mm Mauser, 6000 Austrian 8mm Manlicher, 13347 singly Italian 11-mm Vetterli), 16,5 million different rifle cartridges. The vessel arrived in Cartagena on October 4.

Loading tanker Campeche According to the military cargo was determined to send another 6 September 1936 IV Stalin a telegram from Sochi to Moscow LM Kaganovich:

"It would be good to sell 50 pieces of SB Mexico to Mexico immediately resold them to Spain. You could also pick up 20 people of our good pilots, so they performed in Spain fighting functions, and at the same time taught flights on the SAT Spanish pilots. Consider the case quickly. It would be the same way to sell 20 thousand rifles, machine guns and a thousand million 20 cartridge. It is only necessary to know the gauges.

Stalin. Number 34. 6 / 1H.36 city "

Transport Y-2 - Soviet ship "Komsomol" - with 50 T-26 tanks on board came from Theodosia October 4, 1936 and arrived in Cartagena 12 October.September 29, 1936 at a meeting of the Politburo of the CPSU (b) adopted a formal decision to have surgery «X»:

"NGOs Question

a) approve the plan of operations for the delivery of personnel and special machines in the "X", the full implementation of entrusting operations to Comrades Uritskogo [Chief Intelligence Directorate of the NKO] and Sudyin [acting People's Commissar of Foreign Trade];

b) To conduct a special operation to release the Intelligence 1,910,000 Soviet rubles and 190 thousand dollars. "